Method and apparatus for regulating patient temperature by irrigating the bladder with a fluid

ABSTRACT

A method and apparatus is provided for heating or cooling at least a selected portion of a patient&#39;s body. The method begins by inserting a catheter through the urethra and into the bladder of the patient. A heated or chilled fluid is conducted through a supply lumen of the catheter and into the bladder. The fluid is evacuated from the bladder through a return lumen of the catheter. Finally, a quantity of urine is monitored which flows out of the bladder and through the return lumen of the catheter. The rate of fluid flowing through the supply lumen of the catheter may be adjusted in a manner that is based at least in part on the monitored quantity of urine flowing out of the bladder

RELATED APPLICATIONS

[0001] This application is a continuation of co-pending U.S. patentapplication Ser. No. 09/827,010, filed on Apr. 5, 2001, entitled “MethodAnd Apparatus For Regulating Patient Temperature By Irrigating TheBladder With A Fluid” which is a continuation-in-part of U.S. patentapplication Ser. No. 09/586,000, filed on Jun. 2, 2000, entitled “MethodFor Determining The Effective Thermal Mass Of A Body Or Organ Using ACooling Catheter,” and claims priority to U.S. Provisional PatentApplication Serial No. 60/195,609, filed Apr. 6, 2000, entitled “BladderCooling for Total Body Therapeutic Hypothermia”, and U.S. ProvisionalPatent Application Serial No. 60/270,525, filed Feb. 21, 2001, entitled“Method And Apparatus For Regulating Patient Temperature By IrrigatingThe Bladder With A Fluid”, all of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] I. Field of the Invention

[0003] The present invention relates generally to the modification andcontrol of the temperature of the body. More particularly, the inventionrelates to a method for controlling body temperature by irrigating thebladder with a working fluid.

[0004] II. Description of the Related Art

[0005] Organs in the human body, such as the brain, kidney and heart,are maintained at a constant temperature of approximately 37° C.Hypothermia can be clinically defined as a core body temperature of 35°C. or less. Hypothermia is sometimes characterized further according toits severity. A body core temperature in the range of 33° C. to 35° C.is described as mild hypothermia. A body temperature of 28° C. to 32° C.is described as moderate hypothermia. A body core temperature in therange of 24° C. to 28° C. is described as severe hypothermia.

[0006] Patients may require pre or post-operative cooling for a varietyof reasons, including, for example, treatment of a malignant hypothermiacrisis and induction of therapeutic hypothermia for neurosurgery.

[0007] Catheters have been developed which are inserted into thebloodstream of the patient in order to induce total body hypothermia.For example, U.S. Pat. No. 3,425,419 to Dato describes a method andapparatus of lowering and raising the temperature of the human body. TheDato invention is directed towards a method of inducing moderatehypothermia in a patient using a metallic catheter. The metalliccatheter has an inner passageway through which a fluid, such as water,can be circulated. The catheter is inserted through the femoral vein andthen through the inferior vena cava as far as the right atrium and thesuperior vena cava. The Dato catheter has an elongated cylindrical shapeand is constructed from stainless steel.

[0008] Other less cumbersome catheters have been developed to providecooling intravascularly. For example, a heat transfer element such asdisclosed in U.S. Pat. No. 6,096,068, incorporated herein by referencein its entirety, may be placed in the feeding artery of an organ toabsorb or deliver the heat from or to the blood flowing into the organ.The transfer of heat may cause either a cooling or a heating of theselected organ. The heat transfer element is small enough to fit withinthe feeding artery while still allowing a sufficient blood flow to reachthe organ in order to avoid ischemic organ damage. By placing the heattransfer element within the feeding artery of an organ, the temperatureof the organ can be controlled with less of an effect on the temperatureof the remaining parts of the body. A similar heat transfer device,which is employed for whole body cooling and is disposed in the venousvasculature, is disclosed in U.S. application Ser. No. 09/373,112, alsoincorporated by reference in its entirety.

[0009] While the previously mentioned techniques provide significantthermal control, they require the insertion of a catheter into thevascular system to induce heat transfer between the catheter and theblood stream. This is a relatively invasive procedure, which has anassociated level of risk.

[0010] Accordingly, it would be desirable to provide an effective, lessinvasive method and apparatus for heating or cooling all or part of apatient's body. It would also be desirable to provide an effective, lessinvasive method and apparatus for heating or cooling all or part of apatient's body that could be employed in emergency situations, such ason an ambulance.

SUMMARY OF THE INVENTION

[0011] The present invention provides a method and apparatus for heatingor cooling at least a selected portion of a patient's body. The methodbegins by inserting a catheter through the urethra and into the bladderof the patient. A heated or chilled fluid is conducted through a supplylumen of the catheter and into the bladder. The fluid is evacuated fromthe bladder through a return lumen of the catheter. Finally, a quantityof urine is monitored which flows out of the bladder and through thereturn lumen of the catheter.

[0012] In accordance with one aspect of the invention, the rate of fluidflowing through the supply lumen of the catheter is adjusted in a mannerthat is based at least in part on the monitored quantity of urineflowing out of the bladder.

[0013] In accordance with another aspect of the invention, the fluid isconducted into the supply lumen at a substantially constant flow rate,or alternatively, at a periodically interrupted rate. In one particularembodiment of the invention, the flow rate is less than a flow rate thatwould substantially prevent fluid from flowing from the kidneys to thebladder. In this or another embodiment of the invention, the flow rateof fluid conducted into the supply lumen is substantially equal to aflow rate of fluid being evacuated from the bladder.

[0014] In accordance with another aspect of the invention, the pressureof the fluid flowing into the supply lumen is monitored. The pressure ofthe fluid flowing through the return lumen may be monitored as well.

[0015] In accordance with yet another aspect of the invention, atemperature differential is monitored between the fluid conducted intothe supply lumen and the fluid flowing through the return lumen.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a partially perspective and partially schematic view ofa catheter system including a circulation set constructed in accordancewith the present invention.

[0017]FIG. 2 is a schematic illustration of the circulation set depictedin FIG. 1, showing in particular the flow of the working fluid.

[0018]FIG. 3 shows the distal end of the catheter depicted in FIGS. 1and 2 inserted into the bladder.

[0019] FIGS. 4-8 show different arrangements of the distal end of thecatheter depicted in FIGS. 1 and 2 inserted into the bladder.

[0020]FIG. 9 shows a cross-section of the catheter at a point proximalof the balloon.

[0021] FIGS. 10-12 show various optional dispersion tips located on thesupply orifice of the catheter for distributing fluid throughout thebladder.

[0022]FIG. 13 shows a cross-section of the dispersion tip of FIG. 12.

[0023]FIG. 14A shows a prior art heat exchange system.

[0024]FIG. 14B shows a heat exchange system constructed in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention provides a relatively non-intrusive methodand apparatus for heating or cooling all or part of a patient's body.The invention achieves this result by circulating a heat transfer fluidthrough the patient's bladder 11 (see FIG. 3). Heat transfer via thebladder 11 is advantageous because the bladder 11 is located in theabdominal cavity, surrounded by a variety of organs, and in addition thebladder walls are highly perfused with blood. Further, the abdominalcavity volume includes a substantial portion of the high blood flowvessels the aorta 17 and the inferior vena cava 19. The fluid absorbsheat from or delivers heat through the wall of the bladder 11 and intothe abdominal cavity and the arterial and venous vessels populating thisarea, thereby regulating the temperature of a patient's whole body orone or more selected organs. In particular, the bladder 11 is suppliedwith blood by the superior, middle and inferior vesical arteries, whicharise from the auterior trunk of the intereal iliac artery. As a result,cooling of the internal organs and a considerable amount of blood can beaccomplished without the invasive step of inserting a catheter directlyinto the vascular system.

[0026] In addition, for surgeries requiring more than about two hours toperform, insertion of a catheter into the bladder to monitor urineoutput is a common procedure. Such urethral catheters are commonlytermed “Foley” catheters. A common Foley-type catheter may be the basisfor the design and construction of a catheter according to theinvention. As described below, however, significant modifications may bemade to a common Foley catheter in order to make the same optimum forthe present methods.

[0027]FIG. 1 shows one embodiment of the bladder thermal control system20 constructed in accordance with the present invention. The systemincludes a catheter 100, control system 26, and a circulation set 28partially housed by the control unit system 26. The control system 26may be equipped with an output display 36 and input keys 40 tofacilitate user interaction with the control system 26. While FIG. 1shows a fairly large and relatively complex control system 26, thecomplexity of the same depends on the application to which the same isput. For example, for a rewarming application, the control system 26 maybe a simple Mallinkrodt Blood and Fluid Warmer, as manufactured byMallinkrodt Medical of St. Louis, Mo.

[0028] Alternatively, for certain applications, such as rewarming ormaintaining normothermia during a surgery or other procedure, the natureof the heat exchanger used within the control system may be simple, suchas a simple resistive heat exchanger or thermo-electric heat exchanger.

[0029] The catheter 100, which may employ a design similar to that of aFoley catheter, for example, is configured for insertion into theurethra. The proximal end of the catheter 100 includes a manifold 105having an inlet port 102 and an outlet port 104 on its proximal end. Asupply lumen 106 and a return lumen 108 are connected to a port locatedon the distal end of the manifold 105. At the catheter's distal end thesupply and return lumens 106 and 108 respectively terminate in supplyand return orifices 110 and 112. The catheter may have a diameter of,e.g., 18 F or another size as dictated by the requirements of the user.

[0030] The supply orifice 110 may include an optional dispersion tip. InFIG. 3, both a supply orifice 115 and a dispersion tip 116 are shown,although in practice typically only one or the other would be used. Thesupply orifice 110 may cause the fluid to emerge in a direction parallelto the axis of the catheter (supply orifice 110) or perpendicular to thesame (supply orifice 115). These aspects are discussed in more detailbelow in connection with FIGS. 4-8.

[0031] Whether a dispersion tip is used or not, the distal tip or supplyorifice of the catheter may be made of a very soft material so as tominimize tissue damage of the urethra upon insertion. The same may becoated with various materials to minimize deleterious coating ofundesired biological materials on the tip during or after insertion.

[0032] The supply and return lumens 106 and 108 may be formed from apair of concentric flexible tubes so that the supply lumen 106 may beconcentrically located within the annular return lumen 108. Of course,the same may also be non-coaxial as dictated by the requirements of theuser. As shown in more detail in FIG. 3, when the catheter 100 isproperly inserted into the urethra its distal end is located in thebladder. Fluid is conducted into the bladder from the supply lumen 106via supply orifice 110. Fluid is conducted out of the bladder 11 via atleast one return orifice 112 and into return lumen or lumens 108. AsFIG. 3 indicates, in some embodiments of the invention the supplyorifice 110 is spatially separated from the return orifices 112 so thatfluid has an opportunity to thoroughly irrigate the bladder 11 beforereturning through the return orifice 112.

[0033] As in a conventional Foley catheter, the catheter 100 may includea balloon 14 (see FIGS. 3 and 4) near its tip to prevent its expulsionfrom the urethra. The balloon 14 may also serve the purpose of anchoringthe catheter against movement caused by a pulsating working fluidsupply, as may be the case if certain types of pumps are employed todrive the working fluid. The balloon 14 may be inflated by a singleinflation lumen, a dual inflation lumen, or other such lumen as isknown.

[0034] Referring to FIG. 9, one embodiment of a catheter shaft is shownin cross-section. The catheter shaft 123 includes a supply lumen 106 anda return lumen 108. A lumen 122 is also shown for providing a spacethrough which to deliver cabling to pressure monitor 77; however,cabling for pressure monitor 77 may also be provided through amicrocatheter or capillary catheter disposed within the supply lumen 106or the return lumen 108. A separate lumen 125 is also shown for use ininflating and deflating balloon 114. A separate lumen 125 is also shownfor use in delivering various drugs. While four separate lumens areshown in FIG. 9, more or less may be provided depending on therequirements of the user. With reference to FIGS. 1 and 2, an embodimentof the circulation set 28 will now be described. The circulation set 28may include one or more of the following: a fluid reservoir 60, a pump64, a filter 68, a heat exchanger 72, a temperature and pressure sensorassembly 76, supply line 80, and a return line 84. The supply line 80and return line 84 are preferably comprised of one or more pieces oftubing, connectors, etc. joining the aforementioned components of thecirculation set 28. The circulation set 28 supplies, filters,circulates, and monitors the temperature and pressure of the heattransfer fluid for the catheter 24.

[0035] In one embodiment, the fluid reservoir 60 is a modified IV bagmade of PVC filled with saline. Since the typical bladder volume isabout 500-750 cc, the volume of the fluid reservoir 60 should be greaterthan about 1000 cc. In this way the entire working fluid, as well asurine produced during the procedure, can be contained within thereservoir 60. Other working fluids besides saline such as, but notlimited to, isotonic solutions, Ringer solution, and the like may beused. Various other solutions may be employed, including those that actto neutralize the proteins inherent in urine. In this way, when thecombination of working fluid and urine is recirculated back into thebladder, the danger of infection is minimized.

[0036] The fluid reservoir 60 is used to prime the lines 80, 84 andlumens 106 and 108 of the catheter 100. For example, the system may beprimed with 0.9% saline, and then the pump speed adjusted such that thedriving pressure of the working fluid (by the pump) plus the returnvacuum cancel out. Then, if a higher flow rate is desired, thecollection bag, reservoir 60, may simply be raised higher. The fluidreservoir 60 includes a supply or inlet tube 90 that communicates at aninlet 91 with the return line 84 outside of the reservoir 60 andcommunicates at an opposite end or outlet 92 with an inside 94 of thereservoir 60. The fluid reservoir 60 also includes a return or outlettube 96 that communicates at one end with the supply line 80 outside ofthe reservoir 60 and communicates at an opposite end, i.e., at an inlet98, with the inside 94 of the reservoir 60.

[0037] The reservoir 60 may typically have a pressure of about 75 mm Hg(1.4 psi), although the same may be pressurized to achieve higherpressures, e.g., 300 mm Hg (5.6 psi).

[0038] The filter 68 is preferably a 5-micron filter carried by male andfemale housing members. The filter 68 removes impurities from thecirculating heat transfer fluid. In other embodiments of the circulationset 28, the circulation set 28 may include more than one filter 68, thecirculation set 28 may include no filters 68, or the filter 68 may be apart of one or more components of the circulation set.

[0039] The heat exchanger 72, which is used to heat or chill the fluidsupplied to the catheter, may be any of a variety of conventionallydesigned heat exchangers. As noted above, the heat exchanger 72 mayemploy a resistive heater, a microwave heater, a thermoelectric device,a closed-circuit temperature control system, etc.

[0040] In another embodiment, a height differential ‘h’ may be employedbetween an additional fluid reservoir, such as an elevated IV bag, andthe catheter. The purpose of the pump would then be to pump thecombination working fluid and urine up to the additional fluidreservoir. This has a benefit in that many physicians, such asurologists, are more comfortable reading bladder pressure as centimetersof water. For example, many urologists use, as a rule of thumb, about10-20 centimeters of water as a safe bladder pressure. The height of thetop of the water in the IV bag, referenced to the approximate height ofthe bladder, can then be easily visually used as a measure of bladderinflation pressure.

[0041] One difficulty with this technique may be that, to force asufficient quantity of working fluid through a catheter of reasonablesize entails placing the IV bag at a height much higher than 10-20centimeters, limiting the locations where the technique can be employed.

[0042] The control of the speed of pump 64 may be primarily given tocontrol circuit 126, and a primary determinant of the pump speed may bethe core body temperature as determined by a temperature monitor 128.The temperature monitor 128 may be an esophageal monitor, a tympanicmonitor, or any other type of temperature monitor as is known in the artwith which core body temperature may be monitored. In other words, themeasured patient temperature may be the primary parameter on whichdepends the speed of pump 64. The value of the internal bladder pressuremay also be used as a safety control to ensure that a dangerousover-pressure situation never arises, as is described in more detailbelow.

[0043] More specifically, if ΔT=Target Temperature−Core Temperature,then ΔT and the internal bladder pressure may determine the pump speedand the level of “valving” of a pinch valve 65. For example, a “span”may be defined which corresponds to a ΔT small enough that very closecontrol by control circuit 26 must occur in order to prevent overshoot.If ΔT>the span, i.e., the target temperature is relatively far from thecore temperature, then the pump speed is maximized and the pinch valve65 actuated to maintain the pressure of working fluid in the bladder 11.In this mode, the maximum amount of heating (or cooling) would occur.The pinch valve 65 is actuated to ensure that the bladder is notover-pressurized, as may be measured directly or inferred by a techniquedescribed below. If AT is between zero and the span, then the pump speedmay be set proportional to ΔT, and/or the pinch valve 65 may beregulated to maintain the pressure of the working fluid in the bladder11. In fact, due to a lessened pump speed, the pinch valve 65 mayrequire significant opening in order to maintain the pressure of theworking fluid in the bladder 11. This is because it has been noted thatthe pressure of the working fluid in the bladder must be maintained inorder to maintain a satisfactory heat transfer rate.

[0044] As noted above, a pressure sensor 77 may be employed to measurethe pressure of the working fluid in the bladder 11. This pressuresensor 77 may be provided through a throughlumen in either thesupply/inlet lumen or the return/outlet lumen, and may comprise astandard medical-grade pressure transducer. This pressure sensor 77 maybe referenced to a core pressure monitor 127 (the transducer of which isnot shown in FIG. 2) and both may provide signals to the control circuit126. In particular, the measured bladder pressure may be employed, whenΔT is less than the span, to control the level of valving of pinch valve65 in order to maintain the bladder pressure at as high a level as issafe and effective for heat transfer to occur. A typical operatingpressure for safe use in the bladder has been quoted in some sources asbeing in the range of 0.2 to 0.3 psi. It is also noted that a typicalureter transport pressure, i.e., the maximum bladder pressure whichwould allow an influx of urine from the ureters, has been suggested tobe about 20-60 cm H₂O or about 0.28-0.85 psi. Thus, this value, ifproperly assessed and measured, may also be used as a maximum pressure.For example, a conservative approach may be to use the lesser of theallowed pressures as a maximum.

[0045] The pressure sensor 77 and the control circuit 126 may bedesigned such that if a pressure higher than a predetermined value isencountered in the bladder, the pump 64 shuts down or the valve 65completely closes or both. Other failsafe procedures may also beemployed.

[0046] The pressure sensor 77 may be referenced to an internal pressuremeasured at another location, such as the heart line, etc. In abdominalsurgery, such a reference pressure may be neglected.

[0047] As shown in FIGS. 4-8, the pressure sensor 77 may be located invarious locations with respect to the supply orifice 110. In FIG. 4, thepressure sensor 77 and the supply orifice 110 are shown in roughly thesame location at the distal tip of the catheter. The pressure sensor 77may also be proximal of the distal tip, as shown in FIG. 5. The samecould be true in the case where a side supply orifice 115 is employed(FIG. 6). Alternatively, where a side supply orifice 115 is employed,the pressure sensor 77 may be located at the distal tip of the catheter(FIG. 7). If a dispersion tip 116 is employed, as is shown schematicallyin FIG. 8, the pressure sensor 77 may be located at the distal tip ofthe catheter or proximal of the distal tip of the catheter.

[0048] As noted above, the pump 64 is provided to draw the heat transferfluid from the fluid reservoir 60 and push the fluid into the bladder11. The flow rate of the heat transfer fluid is then determined by thespeed of pump 64 as well as the state of valve 65. If the fluid columnis continuous from the return ports (in the bladder) to the reservoir60, a height h below the bladder, an effective pressure of

p=ρgh−Ku ²

[0049] where K is the head loss coefficient of the drain path. Inpractice, maintaining a complete fluid column in the drain path resultsin effective draining of the bladder. To control the amount of draining,a valve 65′ may be disposed in the drain path. Valve 65′ may be usedeither in combination with valve 65 or in place thereof.

[0050] In this system, a specified flux of working fluid may be suppliedto the bladder. Valve 65′ can be actuated to obtained the desiredbladder pressure and volume. If the supply flux is less than the drainflux, when the valve 65′ is completely open, then forp_(bladder)<p_(maximum), the system will not overpressure the bladder.

[0051] The temperature and pressure sensor assembly 76 is used in oneembodiment for measuring the temperature and the pressure of the heattransfer fluid in the supply line 80 before it enters the catheter 24,and measuring the temperature and the pressure of the heat transferfluid in the return line 84, after it leaves the catheter 24. Asdescribed in more detail below, one or both of these measurements areimportant for determining not only the heating or cooling efficiencythat can be achieved with the catheter 100, but also to ensure that thepatient's bladder 11 is not irrigated at such a high rate, or subjectedto such a high pressure, that renal failure occurs. The temperature andpressure sensor assembly 76 includes thermocouples and pressuretransducers for respectively measuring the temperature and pressure ofthe fluid, and may also include associated electronics.

[0052] Signals from the temperature and pressure assembly 76 areprovided to control the control circuit 126 within control unit 26(FIGS. 1 and 2). As noted above, this information is used by controlunit 26 as feedback to control the throughput of pump 64 (if included incirculation set 28), which in turn determines the flow rate of the fluidbased on input parameters supplied to the control unit 26 via user inputkeys 40. The control unit 26 may also determine the rate of heattransferred to and from the working fluid by the heat exchanger 72.

[0053] The temperature and pressure sensor assembly 76 may includealarms that shut down the system if a dangerous situation arises. Forexample, a maximum safe temperature of working fluid has been quoted asbeing about 45° C. If this temperature were exceeded, the system may bedesigned to shut itself down or even turn itself off. Alternatively, ahigh temperature may be allowed, but only for a short predeterminedperiod of time.

[0054] In another reference source, the mucosa in the bladder lining hasbeen noted as being damaged after exposure to 430C working fluid forfour hours. The “pain threshold” has been noted as 42.5° C. A “mixedfluid” temperature may be defined as that which exits the bladder, andcorresponds to the temperature of fluid after the effect of mixing withexisting fluid in the bladder as well as with the urine. Rather thanrelying for safety on a lowering of the working fluid temperature uponentering the bladder, another suitable procedure may be to set thetemperature of the working fluid as high as possible, without damagingtissue, for its entry into the bladder. This would correspond to amaximum heat transfer condition. That is, the effect of mixing can onlybe to lower the temperature and lessen the heat transfer. Then the flowrate may be set as high as possible, again without damaging the tissue.A typical flow rate may be, e.g., about 4-5 cubic centimeters of workingfluid per second. Animal experiments have shown that such flow rates maylead to about 100-120 Watts of cooling, at 2½ to 3½° C. per hour, for ananimal of 40 kg. Animal experiments have also shown that such flow ratesmay lead to about 40 Watts of heating for an animal of 40 kg.

[0055] In a cooling regime, a suitable range of extreme low temperaturesmay be about 10-12° C. In particular, these temperatures would be forthe temperature of the working fluid as it enters the bladder. In thisregime, the temperature may be chosen to be high enough so as to notcause uric acid crystallization, etc. The circulation set 28 depicted inFIGS. 1 and 2 recirculates the heat transfer fluid so that it flowsthrough the bladder 11 a multiple of times. In this case the heattransfer fluid would include urine that has accumulated in the bladder11 and been conducted through the return lumen of the catheter. In otherembodiments of the invention, however, the circulation set 28 maycontinuously replenish the supply of heat transfer fluid so that thebladder 11 is irrigated with fresh heat transfer fluid. In this case theheat transfer fluid is disposed of after being flushed from the bladder11 by the catheter.

[0056] It is generally important during many surgical procedures tomonitor the flow of urine to assess the overall physiologic balance ofthe patient and to ensure that renal failure does not occur. That is, ifa patient is receiving an infusion of a given amount of fluid, urinemonitoring should be performed to ensure that the patient is properlyprocessing the fluid. Dangerous situations could arise if the patientwere not maintaining proper hydration or if the patient were taking influid other than through the vasculature or the gastrointestinal system,such as the lungs, for example. This so-called “third spacing” of thefluid may lead to a hazardous situation warranting immediateintervention. In addition, renal ischemic injury such as acute tubularnecrosis (ATN) can arise. If this occurs, the patient may be given theopportunity to eliminate the fluid on his or her own. That is, if thekidneys 15 (FIG. 3) fail, they may simply flush out the remaining fluid,after which no more fluid would be produced.

[0057] The typical urine output from a 70 kg patient has been measuredto be about 70 ml/hour up to about a liter per day (0.6 cc/hr/kg). Ofcourse, these numbers may vary according to the patient. Accordingly,during the procedure the volume of fluid returning from the bladder 11in the circulation set should be monitored to ensure that it increasesat the expected rate. If the volume of urine does not increase asexpected, the patient may be undergoing renal failure and the procedureshould be stopped so that appropriate action can be taken.

[0058] The urine output volume may be measured in a number of differentways. For example, in one embodiment of the invention in which the heattransfer fluid is recirculated, the urine output may be monitored simplyby observing the change in fluid level in the fluid reservoir 60.Alternatively, or in addition thereto, the fluid level may beelectronically or optically detected by a sensor so that it can bemonitored by the control unit 26.

[0059] If the fluid is disposed of after being flushed from the bladder11, control unit 26 can determine the quantity or rate of urine outputsimply by measuring the differential between the quantity or rate offluid flowing into the bladder 11 and flowing out of the bladder 11 oncethe bladder 11 has been initially filled.

[0060] In some embodiments of the invention the control unit mayautomatically adjust the fluid flow rate in response to the measuredurine volume. Some factors that may be considered in determining theappropriate relationship between the fluid flow rate and the urinevolume will be presented below.

[0061] The volume of fluid supplied by the catheter and residing in thebladder 11 must not be so great that it upsets the physiologic balancein the bladder 11. In particular, the volume of fluid should not be sogreat that it exerts a pressure on the walls of the bladder 11 thatprevents the flow of urine from the ureters 13 (FIG. 3) into the bladder11. This pressure should typically be less than about 0.28-0.85 psi. Oneway of ensuring that this does not occur is to monitor the urine flow inthe manner previously described. However, another technique may be todirectly measure the pressure of the fluid in the supply line before itenters the catheter and in the return line after it leaves the catheter.It can be shown that, in the steady state, where the small urineproduction is ignored, that:$p_{BLADDER} = {\frac{p_{SUPPLY} + p_{RETURN}}{2} - \frac{{\Delta \quad {p_{SUPPLY}(Q)}} - {\Delta \quad {p_{RETURN}(Q)}}}{2}}$

[0062] where P_(SUPPLY) is the supply pressure, P_(RETURN) is the returnpressure, P_(BLADDER) is the bladder pressure, Q is the supply andreturn heat flux (in the steady state), Δp_(SUPPLY) (Q) is the pressuredrop on the supply lumen, and Δp_(RETURN) (Q) is the pressure drop onthe return lumen.

[0063] In the case of identical supply and return lumens, this reducesto (as Δp_(SUPPLY) (Q)=Δp_(RETURN) (Q))$p_{BLADDER} = \frac{p_{SUPPLY} + p_{RETURN}}{2}$

[0064] While it may be only strictly necessary to monitor either theurine flow rate or the pressure of the fluid, in general it will beadvantageous to monitor both flow rate and pressure. In this way, theoccurrence of both overpressurization of the bladder 11 and renalfailure can be detected. If only pressure is monitored, the occurrenceof renal failure may be missed. If only flow is monitored, the bladdermay become over-pressurized.

[0065] The fluid may be provided to the supply lumen in a continuous,constant flow or as a pulsed flow of fluid. The pulsed flow may be aflow that is either intermittently interrupted or simply reduced in rateon an intermittent basis. A pulsed flow rate will allow urine that hasaccumulated in the bladder 11 to be flushed out. For example, the flowrate may be pulsed so that the bladder 11 is flushed at a regularinterval, e.g., every few minutes. The present invention alsocontemplates more complex flow rate patterns such as periodic andaperiodic oscillatory patterns, for example. If a constant flow is used,it should be sufficiently low to ensure that the pressure in the bladder11 is not so great that urine cannot be flushed from the bladder 11.That is, the bladder 11 pressure should be less than the pressure in theureter 13 so that urine flow from the kidneys 15 to the bladder 11 isnot prevented. Of course, in many cases it will be desirable to maintainas great a flow of fluid as possible to maximize the rate of heatexchange. If a pulsed flow is used, the pressure exerted upon thebladder 11 by each pulse may exceed the pressure that can be used in acontinuous flow. However, the duration between the pulses should besufficiently great so that urine flows out of the bladder 11 to allowdrainage of the kidneys 15. The flow rate can be controlled by controlunit 26 based on the information received from the temperature and/orpressure assembly 76, the values of the user input parameters receivedvia user input keys 40, the value of pressure in the bladder measured bypressure monitor 77, or the volume or rate of urine flow out of thebladder 11.

[0066] Returning to FIGS. 3-8, which show the distal end of the catheterinserted in the bladder 11, a variety of different tips 116 may beprovided over supply orifice 110 to facilitate distribution of the fluidin the bladder 11 so that the bladder 11 is thoroughly irrigated. Forexample, as shown in FIG. 10, tip 116 a may be a diffuser thatdistributes the fluid in substantially all directions. The diffusing tip116 a may be formed, for example, from a porous material or animpermeable material having a series of orifices distributed over itssurface.

[0067]FIG. 11 shows another tip design that employs a floating ballvalve 116 b. Floating ball valve 116 b includes a slidable ball 117whose movement is constrained by cage 118, which extends outward fromthe supply orifice 110. When fluid exits the supply orifice 110, thefluid exerts pressure on the slidable ball 117 so that the ball movesaway from the orifice 110, forcing the fluid to flow out of the valve ina dispersed manner. Moreover, the floating ball valve 116 badvantageously prevents substantial amounts of fluid from flowing backinto the supply orifice 110 when no fluid is flowing up through thecatheter. This is because when no fluid is exiting supply orifice 110,any backflow of fluid into the supply orifice 110 will cause the ball117 to move toward, and close off, the orifice 110 as a result of thefluid's viscosity and the resulting region of reduced pressure thatdevelops between the ball 117 and the supply orifice 110.

[0068]FIG. 12 shows yet another embodiment of the invention that employsa deflector tip 116 c that has a surface 119 opposing the plane of thesupply orifice 110, which deflects the fluid as it exits the orifice 110so that it is distributed over a complete 3600 region. The deflector tip116 c, which is preferably formed from a pliable material, is fixed toan insert (not shown) positioned in the supply orifice 110.

[0069]FIG. 13 illustrates a cross-section of the tip of FIG. 12, andshows four roughly perpendicular fluid paths 165 emerging from foursupply lumens 166. The four supply lumens 166 may all emerge themselvesfrom supply lumen 106. In other words, supply lumen 106 may be splitinto four separate lumens 166 to allow four mutually perpendicular orindependent flows 165 to emerge. As the insertion of a Foley-typecatheter is generally uncomplicated, and can be performed by nurses oremergency personnel, embodiments of the invention may be implemented onan emergency vehicle such as an ambulance. One aspect allowing this maybe inclusion in certain embodiments of a compressed gas system to cool acirculating fluid. It is again noted that in heating embodiments asimple resistive heater may be employed.

[0070] Prior chiller units employing a closed cycle evaporative gassystem were complicated, expensive, and difficult to simplify andminiaturize for use in a portable transportable system. Further, theyrequired significant electrical power to operate. For example, referringto FIG. 14A, a prior art refrigeration system 200 is shown. Such asystem is exceedingly well-known, and includes a pump 202, a heatexchanger 204, a restriction valve 208, and an apparatus 206 to exhaustheat to a temperature bath. In this system, as is known, a liquid to gasheat exchanger transfers heat from the working fluid to the cold side ofan evaporative chiller.

[0071] A system 201 according to an embodiment of the present inventionis shown in FIG. 14B. In this figure, a source of compressed gas 218 isvalvably coupled via valve 220 to an optional restriction valve 222 to aheat exchanger 224. A working fluid output for, e.g., cold workingfluid, is labeled by outlet 214. A working fluid input for, e.g., hotworking fluid, is labeled by inlet 216. An exhaust to the environment isshown as exhaust 226.

[0072] In system 201, a compressed gas from source 218 is expandedadiabatically through a valve. The expansion results in a reducedtemperature gas that absorbs heat from the working fluid in theliquid-to-gas heat exchanger 224. The heated, expanded gas is thendiscarded to the environment via exhaust 226. A additional temperaturereduction in the expanded gas may be achieved by the phase change fromthe storage pressure to the expanded pressure.

[0073] Gases which may be useful in embodiments of the inventionemploying adiabatic expansion include nitrogen, carbon dioxide, etc.Gases which may be useful in embodiments of the invention employingadiabatic expansion with a phase change include nitrous oxide.

[0074] Of course, it should be noted that the above portable heatexchange system may be employed not only in the above bladder coolingembodiment but may also be employed as a heat exchange system forvarious other heat exchange catheters, including that disclosed in U.S.Pat. No. 6,096,068, incorporated above by reference in its entirety, orthat disclosed in U.S. application Ser. No. 09/373,112, alsoincorporated by reference in its entirety.

[0075] While the invention herein disclosed is capable of obtaining theobjects hereinbefore stated, it is to be understood that this disclosureis merely illustrative of the presently preferred embodiments of theinvention and that no limitations are intended other than as describedin the appended claims. For example, the invention can be used in a widevariety of settings, e.g., in the applications of general surgery, andin particular lengthy surgeries, orthopedic and back surgery, livertransplants, etc.

1. A catheter, comprising: a manifold having a proximal end with atleast first and second input ports and a distal end with at least firstand second output ports; at least first and second flexible tubesdefining a supply lumen and a return lumen, respectively, said first andsecond flexible tubes having proximal ends removably connectable to theoutput ports of the manifold and having distal ends with a supply andreturn orifice, respectively; and a dispersing element associated withthe supply orifice for dispersing fluid exiting the supply orifice intoa portion of the body.
 2. The catheter of claim 1, wherein saiddispersing element is a diffusing element.
 3. The catheter of claim 1,wherein said dispersing element is a floating ball valve.
 4. Thecatheter of claim 1, wherein said dispersing element is a deflectingelement.
 5. The catheter of claim 1, wherein said return orifice isspatially separated from said supply orifice.
 6. The catheter of claim5, wherein said spatial separation between said supply and returnorifices is sufficient to prevent a substantial flow of fluid directlyfrom said supply orifice to said return orifice.
 7. The catheter ofclaim 1, further comprising an inflatable balloon for maintaining anoperative position of said tubes when inserted into a patient.
 8. Thecatheter of claim 1, wherein said first and second flexible tubes areconcentrically oriented with respect to one another.
 9. A Foley catheterfor heating or cooling at least a selected portion of a body,comprising: a catheter for irrigating and evacuating the bladder with aheated or chilled fluid, the catheter including: a manifold having aproximal end with at least first and second input ports and a distal endwith at least first and second output ports; at least first and secondflexible tubes defining a supply lumen and a return lumen, respectively,said first and second flexible tubes having proximal ends removablyconnectable to the output ports of the manifold and having distal endswith a supply and return orifice, respectively; means, coupled to thecatheter, for controlling at least one measurable parameter of the fluidirrigating the bladder; and means for monitoring at least one parameterselected from the group consisting of: the at least one measurableparameter of fluid flowing out of the bladder while it is beingirrigated, a core temperature of the body, and a pressure of thecombined heated or chilled fluid and urine in the bladder.
 10. Thecatheter of claim 9, further comprising an inflatable balloon coupled tosaid catheter for maintaining an operative position of said catheterwhen inserted into a patient.
 11. The catheter of claim 9, wherein themeans for monitoring the core temperature of the body is an esophagealtemperature probe.
 12. The catheter of claim 9, wherein the means formonitoring the core temperature of the body is a tympanic temperatureprobe.
 13. The catheter of claim 9, wherein the means for monitoring thepressure of the bladder is a pressure transducer mounted adjacent thedistal tip of the catheter.
 14. The catheter of claim 9, wherein the atleast one measurable parameter of fluid flowing out of the bladder isthe output of urine.
 15. The catheter of claim 9, further comprising asensor for measuring the output of urine.
 16. The catheter of claim 15,wherein the sensor is an optical sensor.